The present invention relates to a sundial.
As the position of the Earth relative to the sun changes as the Earth rotates about its axis, the sun appears to move from east to west in the sky at approximately 15xc2x0 per hour. Traditional sundials utilise this change in solar position to indicate the time of day by relying in general on a gnomon to cast a shadow onto a flat graduated surface. Such traditional sundials are normally constructed for outdoor use and a visible indication of the time of day is given by the proximity of the shadow to the various hour line graduations. In general, there is a limited range and variety of sundial constructions available due in part to the technical challenges involved in correlating solar position to a recognisable indication of the time of day. Moreover traditional sundials are generally unsuitable for indoor use. The present invention is based on a significant departure from the traditional sundial constructions which may be used indoors.
Thus viewed from one aspect the present invention provides a sundial for indicating the time of day using the position of the sun having a labyrinthine body comprising;
a first face capable of admitting a ray of light from each solar position in a substantially southeriy direction,
a second face adapted to visibly receive said ray of light;
wherein said labyrinthine body is provided with a plurality of pathways connecting said first and said second face, each pathway being adapted either to transmit said ray of light from an entry end at the first face. to an exit end at the second face or to absorb said ray of light depending on the solar position,
whereby the second face indicates visibly the time of day.
The sundial of the invention is particularly suitable for indoor use for example in front of a south facing window.
In a preferred embodiment, the labyrinthine body comprises a plurality of discrete layers. Each layer may comprise one or more pathways (eg tunnels, channels and the like) capable of transmitting a ray of light from a specific solar position (or a number of specific solar positions) from an entry end to an exit end on first and second faces of the sundial respectively.
In a particularly preferred embodiment, the labyrinthine body comprises at least five discrete horizontal layers. The first, third and fifth layers each comprise a pathway constructed so that the exit ends are horizontally positioned substantially directly above one another on the second face of the sundial. The second and fourth layers each comprise three pathways constructed so that the exit ends are vertically positioned on the second face of the sundial. Whilst the first, third and fifth layers may be generally narrow, the second and fourth layers are generally thicker.
Whilst five layers are generally the minimum required in accordance with the above embodiment, any number of other layers may be added as required. For example, seven layers is preferable and in this case the outermost layers are provided for capping the five innermost functional layers.
In one embodiment, separating means may be placed intermediate each of the discrete layers making up the labyrinthine body. These may take the form of thin layers of material, the surface of which is preferably.reflective.
The labyrinthine body may have a generally spherical configuration. Alternatively, the labyrinthine body is box-like having a single layer with a plurality of internal walls (eg six). This is an advantageous arrangement in terms of low cost and simplicity of construction and may be used as a wrist watch.
An opaque surface is conveniently positioned on the second face so that light transmitted through the pathways is visible. If desired, a further outer vertical layer of transparent material may be provided to form a face on the sundial.
A ray of light transmitted to the exit end may illuminate a pre-prepared surface at the second face. For example, the pre-prepared surface may comprise a plurality of exit ends patterned in the manner of a timepiece. Preferably, the timepiece is of the numeric type (eg digital-like or Roman numerals) permitting the time of day to be visibly indicated as the appropriately illuminated numeral on the second face. For example, the overall disposition of horizontal and vertical exit ends at the second face may comprise a box like xe2x80x9c18xe2x80x9d configuration which with appropriate illumination of one or more exit ends allows each of the requisite numerals 1 to 12 to be visibly indicated. Alternatively.there may be a series of horizontal, vertical and angled exit ends at the second face which with appropriate illumination permit each of the desired Roman numerals to be illuminated (eg the Roman numerals between IX in the morning to V in the evening).
In a further embodiment of the invention, the second face of the labyrinthine body may be arranged as a clock face. For this purpose, the labyrinthine body may be composed of a plurality of discrete layers comprising pathways constructed so that one or more exit ends illuminate an appropriate hour marker on the face of the clock (in accordance with the appropriate solar position).
By way of example, for a southerly directed first face at 1 pm British Standard Time, the pathways will be arranged to transmit rays of light, from the specific solar position at which the rays are incident at 90xc2x0 to the first face so that the numeral one, I or an appropriate marker positioned at one o""clock on a clock face will be illuminated. At all other times, the numeral one, I or marker remains non-illuminated. A different pathway transmits light rays for each hour (ie in accordance with each solar position). Preferably the pathways will be positioned at angles differing by factors of about 15xc2x0.
Viewed from a yet further aspect the present invention provides a sundial for indicating the time of day using the position of the sun comprising a holographically prepared surface (eg a holographic plate) with a plurality of images which are activated by light from a specific solar position (or number of specific solar positions).
In a preferred embodiment, a holographic plate may comprise a series of images which are composed so that they are only visible in natural light when it is incident from a""specific direction. In this manner, a holographically prepared surface may be used to indicate the time through either a series of numbers or words representing the hours or a series of geometric shapes positioned to indicate the time on some sort of clock face.
Typically the sundial of the invention will be operable between the hours of nine o""clock in the morning and five o""clock in the evening. where appropriate (and particularly where the sundial is mobile eg as a wrist watch), the sundial may need to be provided with means for aligning the sundial in a Southerly direction (or 15xc2x0 East or West of South depending on the time of year and the country of use). For example, a compass may be installed on or in the labyrinthine body.